// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "base/debug/task_annotator.h"

#include "base/debug/alias.h"
#include "base/pending_task.h"
#include "base/trace_event/trace_event.h"
#include "base/tracked_objects.h"

namespace base {
namespace debug {

    TaskAnnotator::TaskAnnotator()
    {
    }

    TaskAnnotator::~TaskAnnotator()
    {
    }

    void TaskAnnotator::DidQueueTask(const char* queue_function,
        const PendingTask& pending_task)
    {
        TRACE_EVENT_WITH_FLOW0(TRACE_DISABLED_BY_DEFAULT("toplevel.flow"),
            queue_function,
            TRACE_ID_MANGLE(GetTaskTraceID(pending_task)),
            TRACE_EVENT_FLAG_FLOW_OUT);
    }

    void TaskAnnotator::RunTask(const char* queue_function,
        /*const*/ PendingTask& pending_task)
    {
        tracked_objects::TaskStopwatch stopwatch;
        stopwatch.Start();
        tracked_objects::Duration queue_duration = stopwatch.StartTime() - pending_task.EffectiveTimePosted();

        TRACE_EVENT_WITH_FLOW1(TRACE_DISABLED_BY_DEFAULT("toplevel.flow"),
            queue_function,
            TRACE_ID_MANGLE(GetTaskTraceID(pending_task)),
            TRACE_EVENT_FLAG_FLOW_IN,
            "queue_duration",
            queue_duration.InMilliseconds());

        // Before running the task, store the program counter where it was posted
        // and deliberately alias it to ensure it is on the stack if the task
        // crashes. Be careful not to assume that the variable itself will have the
        // expected value when displayed by the optimizer in an optimized build.
        // Look at a memory dump of the stack.
        const void* program_counter = pending_task.posted_from.program_counter();
        debug::Alias(&program_counter);

        pending_task.task.Run();

        stopwatch.Stop();
        tracked_objects::ThreadData::TallyRunOnNamedThreadIfTracking(
            pending_task, stopwatch);
    }

    uint64_t TaskAnnotator::GetTaskTraceID(const PendingTask& task) const
    {
        return (static_cast<uint64_t>(task.sequence_num) << 32) | ((static_cast<uint64_t>(reinterpret_cast<intptr_t>(this)) << 32) >> 32);
    }

} // namespace debug
} // namespace base
